The doctors referred 16 emaciated children at risk of dying to their special feeding centre in Maiduguri. One in five of the 15,000 children are suffering severe acute malnutrition, the group found.

"We see the trauma on the faces of our patients who have witnessed and survived many horrors," said Ghada Hatim, head of the Doctors Without Borders mission in Nigeria.

Her team reached Bama on Tuesday following a military convoy from Maiduguri, the Borno state capital that is the headquarters of Nigeria's military campaign.

Though Bama is just 70km southeast of Maiduguri, ongoing clashes between the rebels and government troops make travel unsafe and farmers have not planted crops for 18 months, Dr Christopher Mampula of MSF explained by telephone from Paris.